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endocarp : solid and liquid pyrolysis products analysis
Shirley Duarte Chavez
To cite this version:
Thè
se de
doctorat
NNT
:
2021UP
AST012
Acrocomia aculeata endocarp:
solid and liquid pyrolysis
products analysis
Thèse de doctorat de l’Université Paris-Saclay et de
Universidad Nacional de Asunción
École doctorale n
◦579:
Sciences mécaniques et énergétiques,
matériaux et géosciences (SMEMAG)
Spécialité de doctorat: Génie des Procédeés
Unité de recherche : Université Paris-Saclay, CentraleSupélec, Laboratoire de Génie des Procédés et Matériaux, 91190, Gif-sur-Yvette, France. Référent: CentraleSupélec
Thèse présentée et soutenue à Asunción, le 22 janvier 2021, par
Shirley Johanna Magalí Duarte
Chávez
Composition du jury:
M. Marcelo CASTIER Président & Rapporteur
Professeur, Universidad Paraguayo Alemana de Asunción Professeur, Texas A&M University at Qatar
M. Gérald DEBENEST Rapporteur & Examinateur
Professeur, Institut National Polytechnique de Toulouse
Simone FAVARO Examinatrice
Maitre de Conferences, Agricultural Research Corpora-tion (EMBRAPA)
Mme. Giana ALMEIDA Examinatrice
Maitre de Conferences, AgroParisTech
M. Sergio MOTOIKE Examinateur
Professeur, Universidade Federal de Viçosa, Brazil
M. Patrick PERRÉ Directeur
Professeur (HDR), CentraleSupélec
M. Dario ALVISO Codirecteur
Professeur, Universidad Nacional de Asunción Universidad de Buenos Aires
M. Pin LU Coencadrante
Ingénieur de recherche, CentraleSupélec
Juan Carlos ROLÓN Invité
Professeur (HDR), CentraleSupélec (retraité)
Professeur, Universidad Nacional de Asunción (retraité)
Juan Francisco FACETTI Invité
Mots clés:
Endocarpe de noix de coco, Biomasse lignocellulosique, Bio-huile, Charbon de bois,
Pyrolyse, Modéle cinétique, Combustion, Substituts, Gazéification
Résumé:
La mise en place d’une industrie
biosourcée robuste avec des produits
chim-iques, des matériaux et des carburants de
grande valeur a pour objectif économique de
fournir l’incitation financière nécessaire pour
stimuler son expansion.
L’endocarpe de noix
de coco d’Acrocomia aculeata est un déchet
agro-industriel intéressant qui peut être
util-isé comme matière première pour la production
de ces produits à haute valeur ajoutée, dans
le contexte des bio-raffineries de lignocellulose.
En raison de sa faible teneur en humidité et de
sa teneur élevée en lignine, l’endocarpe peut
être traité via des traitements
thermochim-iques tels que la pyrolyse et la gazéification.
En plus des matières premières, la distribution
des produits dépend aussi des paramètres du
procédé. L’étude de la pyrolyse de la biomasse
ainsi que des caractéristiques de ses produits
dans différentes conditions est essentielle afin
d’identifier le traitement le plus efficace.
Le
but de ce travail est d’étudier la pyrolyse de
l’endocarpe d’A. Aculeata en tant que matière
première pour la production de biocarburants
ou de matériaux tels que la bio-huile et le
char-bon de bois. Afin d’atteindre cet objectif, les
modifications des propriétés de la biomasse ont
été évaluées avant et après 2 heures de pyrolyse
isotherme entre 250 et 550
◦C. Différentes
méth-odes analytiques ont été utilisées pour évaluer
les altérations du produit: analyse élémentaire,
analyses de la surface et de la taille des pores,
visualisation ESEM et SEM/FEG et
détermina-tion de la sorpdétermina-tion dynamique à la vapeur. Des
mesures de perte de masse anhydre ont été
ef-fectuées à l’échelle microscopique pour avoir un
aperçu des mécanismes de réaction. Un
mod-èle cinétique basé sur la méthode de l’énergie
d’activation distribuée a été utilisé pour
repro-duire la perte de masse observée et pour
déter-miner les paramètres cinétiques du processus.
La pyrolyse lente et gazéification de l’endocarpe
Keywords:
Coconut endocarp, Lignocellulosic biomass, Bio-oil, Char, Pyrolysis, Kinetic model,
Combustion, Surrogates and Gasification.
Abstract:
The development of a robust
bio-based industry with high value chemicals,
mate-rials and fuels is of major technical and
economi-cal interest. In the context of the so-economi-called
ligno-cellulose bio-refinery, coconut endocarp of
Acro-comia aculeata is an interesting agro-industrial
waste that can be used as feedstock for the
production of these high value-added products.
Because of its low-moisture and high lignin
con-tents, it can be processed using thermo-chemical
treatments, such as pyrolysis and gasification.
However, the product distribution depends on
the reactor type, the process parameters as well
as the feedstocks.
The evaluation of biomass
pyrolysis behavior as well as its products
char-acteristics under different conditions is essential,
in order to propose the most efficient processes.
The aim of this work is to investigate the
py-rolysis of endocarp of A. aculeata as potential
feedstock to produce biofuel or materials such
as bio-oil and charcoal. In order to achieve this
goal, alterations of its fundamental properties
were evaluated before and after 2h of
isother-mal pyrolysis between 250 and 550
◦C. Different
analytical methods were used to assess the
prod-uct alterations: elemental analysis, surface area
and pore size analyses, ESEM and SEM/FEG
visualization and dynamic vapor sorption
deter-mination. Anhydrous weight loss measurements
have been performed at the microscale to have
an insight into the reaction mechanisms. A
ki-netic model based on the Distributed Activation
Energy Method has been used to reproduce the
observed mass loss and to determine the
pro-cess kinetic parameters.
Moreover, the slow
pyrolysis/gasification of the coconut endocarp
and its chars were carried out under different
conditions, experimentally assessing the
con-version rate and the changes of porosity and
surface area during the process.
In addition,
experimental and numerical combustion studies
of pyrolysis bio-oil from coconut endocarp were
conducted.
Pyrolysis was performed on
tor-refied coconut endocarp and the collected
bio-oils were analyzed by gas chromatography/mass
spectrometry. Based on the GC/MS analysis,
three different blends of toluene, ethanol and
acetic acid representative of the real fuel
chem-istry were proposed as the surrogates to carry
out numerical combustion studies. A chemical
kinetics mechanism for
toluene/ethanol/acetic-acid blends oxidation was developed. This will
be done by combining the chemical model of
Huang et al (2017) for toluene, and that of
Christensen et al (2016) for ethanol/acetic-acid
reactions. The kinetic modeling for bio-oil
oxi-dation was performed using the REGATH code.
The combined model consists of 180 species and
1495 reactions. In order to validate the proposed
model, the work focuses on numerical studies of
the combustion of toluene/ethanol/acetic-acid
blends using 0-D constant-volume auto-ignition
as well as 1-D freely-propagating gaseous
pre-mixed flame configurations.
Different flames
operating conditions such as equivalence ratios,
pressure and temperature were studied. In
con-clusion, our results provide sufficient evidence
for long-term application of this feedstock and
its chars as a solid fuel or raw material for
bio-oil, or in the gasification process.
Université Paris-Saclay
Espace Technologique / Immeuble Discovery
General Preamble
The present work aims to contribute towards the transition to a sustainable
bio-economy. It is important to continue with research studies using
Acro-comia acueleata
as a promising crop to be used in productive systems. This
work focuses on the generation of higher value-added products from A. aculeata
fruit processing wastes (coconut endocarp), using thermo-chemical treatments
and analyzing its products by means of experimental techniques and numerical
modelling. We focus on this feed-stock, since its fruits have a great current
relevance as a raw material for the sustainable generation of vegetable oil of
prominent quality and quantity, biofuels and others bio-products.
This thesis has been carried out in collaboration between the Laboratoire
de Génie des Procédés et Matériaux (LGPM, CentraleSupélec - Université Paris
Saclay, France) and Laboratorio de Mecánica y Energía (LAMEEN, FIUNA
-Facultad de Ingeniería de la Universidad Nacional de Asunción, Paraguay).
This manuscript is written in an article-based form. Two publications
therefore constitute chapters
3
and
6
, with unpublished supplementary
infor-mation included in chapters
4
and
5
. The content of the publications have been
slightly modified from the published versions, according to the general format
of the manuscript and mainly in the Introduction and Materials and Methods
sections of the articles, in order to avoid redundant information to the reader.
The references to the publications are as follows:
• Dario Alviso, Shirley Duarte, Nelson Alvarenga, Juan Carlos Rolón, Nasser
Darabiha. Chemical Kinetic Mechanism for Pyrolysis Bio-oil Surrogate.
Energy Fuels. Volume 32, Issue 10, August 2018, Pages 10984-10998.
<DOI:https://doi.org/10.1021/acs.energyfuels.8b02219>
• Shirley Duarte, Pin LU, Patrick Perré. Kinetic parameters estimation for
coconut endocarp pyrolysis.
To be submitted to Current Opinion in Green and Sustainable Chemistry.
The references of presentations at international conferences and its
con-ference proceedings are as follows:
• Shirley Duarte, Pin Lu, Juan Rolon, Gonçalo Monteiro, Patrick Perré.
Pag. 209. PYRO2016 Conference (21st International Symposium on
Analytical and Applied Pyrolysis), in Nancy, France, on May 9-12, 2016.
<Conference book: PYRO2016>
• Shirley Duarte, Dario Alviso, Nelson Alvarenga, Juan Carlos Rolón. 25TH
European Biomass Conference Exhibition, in Stockholm, Sweden, on
June 12-15, 2017.
<Conference book: EUBCE2017>
• Shirley Duarte, Cassandra Giesbrecht, Pin Lu, Patrick Perré. P2.26. 5th
Green and Sustainable Chemistry Conference, ONLINE, on Nov 10-11,
2020.
Contents
Introduction
1
1 Overview
5
1.1 World energy demand and biofuel policies
. . . .
5
1.2 Biomass as a sustainable resource
. . . .
6
1.3 Biofuels and bio based products — An opportunity
. . . .
12
1.4 Acrocomia aculeata: an alternative oil crop and feedstock for
biorefinery
. . . .
14
1.5 Processes for the conversion of biomass: Thermo-chemical
pro-cesses
. . . .
23
1.6 Knowledge gap
. . . .
42
2 Experimental approach
45
2.1 Study system
. . . .
45
2.2 Coconut endocarp physico-chemical alterations by pyrolysis and
its kinetic analysis
. . . .
47
2.3 Numerical approach: “bio-oil combustion kinetics”
. . . .
54
3 Alteration of physico-chemical characteristics of coconut
en-docarp –Acrocomia aculeata– by isothermal pyrolysis: micro
experiments
65
3.1 Introduction
. . . .
65
3.2 Materials and pyrolysis conditions
. . . .
66
3.3 Analytical methods
. . . .
67
3.4 Results and Discussion
. . . .
70
3.5 Conclusion
. . . .
82
4 Kinetic parameters estimation for coconut endocarp —Acrocomia
aculeata
— thermal degradation in the temperature range of
250-400 °C
85
4.1 Introduction
. . . .
86
5 Slow pyrolysis and gasification of coconut endocarp using H
2O
105
5.1 Introduction
. . . 105
5.2 Experiments
. . . 107
5.3 Results and Discussion
. . . 110
5.4 Conclusion
. . . 115
6 Numerical Combustion Studies of Pyrolysis Bio-oil from
Tor-refied coconut endocarp
117
6.1 Introduction
. . . 118
6.2 Bio-oil obtainment and chemical analysis
. . . 119
6.3 Toluene, acetic acid and ethanol chemical models and
experi-mental data
. . . 125
6.4 Kinetic modeling
. . . 129
6.5 Results and Discussion
. . . 130
6.6 Conclusion
. . . 151
Summary and perspectives
153
Appendixes
157
Appendixes
159
List of Tables
1.1 Main coconut oil industries in Paraguay
. . . .
18
1.2 Higher calorific value of some oil species and typical solids
fu-els, compared with the epicarp, mesocarp and endocarp of A.
aculeata
. Source: [
1
,
2
].
. . . .
22
1.3 Properties of bio-oil and standard methods used in the analysis
[
3
,
4
,
5
,
6
]
. . . .
27
1.4 Properties of charcoal and standard methods used in the analysis
[
3
,
7
]
. . . .
29
1.5 Liquid fuels and bio-fuels characteristics [
8
,
9
].
. . . .
36
1.6 ASTM Burner Fuel Standard D 7544 for Fast Pyrolysis Bio-oil
[
10
,
11
]
. . . .
37
2.1 Properties of coconut endocarp —Acrocomia aculeata—
. . . .
46
3.1 Elemental and proximate analyses of the main components of
biomasses
. . . .
68
3.2 Elemental composition and physical properties for untreated and
char samples
. . . .
73
4.1 Kinetic models for lignocellulosic biomass.
. . . .
88
4.2 Anhydrous mass loss during the heating phase.
. . . .
89
4.3 Kinetic parameters estimated for the multi-step models.
. . . .
94
4.4 Total volatiles released for the three-step model.
. . . .
96
4.5 Kinetic parameters estimated for the DAEM.
. . . 101
5.1 Elemental composition and physical properties for untreated and
char samples [
6
].
. . . 108
5.2 Experimental conditions.
. . . 108
5.3 Gasified samples structural characteristics.
. . . 112
6.1 GC/MS analysis results of Bio-oil.
. . . 123
6.2 Chemical composition of bio-oil: Minority species
. . . 124
reactor, LFS: laminar flame speed, , FR: flow reactors, TR:
tur-bulent reactor, JSR: jet-stirred reactor, LPF: laminar premixed
flames, HCCI: homogeneous charge compression ignition, CFF:
counterflow flame, EA: engine application.
. . . 127
6.5 Forty common species.
. . . 129
6.6 Package 1 (Species H
2, H
20
, HO
2, H
2O
2). Reaction rate
co-efficients given in the form k = AT
nexp(−E/RT )
. Units are
mol cm cal s. Highlighted reactions correspond to those with
similar Arrhenius constants for both models. Superscript
revin
[
12
] corresponds to the reverse reactions constants, as for these
reactions, the reactives in [
13
] correspond to the products in [
12
],
and vice versa.
. . . 131
6.7 Package 2 (Species CO, CO
2, HCO, CH, CH
2, CH
3, CH
4).
Reaction rate coefficients given in the form k = AT
nexp(−E/RT )
.
Units are mol cm cal s. Highlighted reactions correspond to those
with similar Arrhenius constants for both models. Superscript
rev
in [
12
] corresponds to the reverse reactions constants, as for
these reactions, the reactives in [
13
] correspond to the products
in [
12
], and vice versa.
. . . 132
6.8 Package 3 (Species CH
2O
, CH
3O
, CH
2OH
, CH
3OH
, CH
3O
2,
CH
3O
2H). Reaction rate coefficients given in the form k =
AT
nexp(−E/RT )
. Units are mol cm cal s. Highlighted
reac-tions correspond to those with similar Arrhenius constants for
both models. Superscript
revin [
12
] corresponds to the reverse
reactions constants, as for these reactions, the reactives in [
13
]
correspond to the products in [
12
], and vice versa.
. . . 133
6.9 Package 4 (Species C
2H, C
2H
2, C
2H
3, C
2H
4, C
2H
5, C
2H
6).
Re-action rate coefficients given in the form k = AT
nexp(−E/RT )
.
Units are mol cm cal s. Highlighted reactions correspond to those
with similar Arrhenius constants for both models. Superscript
rev
in [
12
] corresponds to the reverse reactions constants, as for
these reactions, the reactives in [
13
] correspond to the products
coefficients given in the form k = AT
nexp(−E/RT )
. Units are
mol cm cal s. Highlighted reactions correspond to those with
similar Arrhenius constants for both models. Superscript
revin
[
12
] corresponds to the reverse reactions constants, as for these
reactions, the reactives in [
13
] correspond to the products in [
12
],
and vice versa.
. . . 135
6.11 Reaction packages, see Tabs. 6.6 to 6.10 for reactions.
. . . 136
6.12 Combined models h: Common reactions constants from Huang
et al. [
13
], C: Common reactions constants from Christensen and
Konnov [
12
]
. . . 136
6.13 Standard deviation of laminar flame speed obtained using schemes
A through L, with respect to the original schemes of Huang et
al. [
13
] (toluene) and Christensen and konnov [
12
] (ethanol and
List of Figures
1.1 World energy consumption by fuel type, 1990-2040 (quadrillion
British thermal units "Btu", 1 Btu = 1.055 kJ). Source:
Inter-national Energy Outlook 2018 - IEO 2018 [
14
].
. . . .
6
1.2 Main components of lignocellulose Biomass (reprinted from
Ru-bin [
15
] with permission).
. . . .
7
1.3 Chemical structure of cellulose.
. . . .
8
1.4 Chemical structure of hemicellulose
. . . .
8
1.5 Main structures present in the lignins from three parts of A.
ac-uleata
fruit by 2D HSQC NMR (reprinted from del Río [
16
] with
permission). A: β − ethers; A’: β − ether structures with
acy-lated (by acetate, benzoate, p−hydroxybenzoate or p−coumarate)
γ−OH; B: phenylcoumaran; B’: phenylcoumarans with p−hydroxybenzoates
acylating the γ−OH; C: resinols; C’: tetrahydrofuran structures
formed by β−β
0-coupling of monolignols acylated at the γ−OH;
D: dibenzodioxocins; F: spirodienones; P_b: benzodioxane −
type piceatannol dimeric structures; P_c: phenylcoumaran−type
piceatannol dimeric structures; V: benzodioxane structures formed
by cross−coupling of piceatannol and a monolignol; I: cinnamyl
alcohol end−groups; I’: cinnamyl alcohol end−groups acylated
at the γ−OH; J: cinnamaldehyde end−groups; pBA: p−hydroxybenzoates;
p
CA: p−coumarates; FA: ferulates; H: p−hydroxyphenyl units;
G: guaiacyl units; S: syringyl units; S’: Cα−oxidized syringyl
units.
. . . .
9
1.6 Main products of a biorefinery.
. . . .
10
1.7 Products from thermochemical biorefineries. Adapted from [
17
].
11
1.8 Potential uses of Acrocomia fruit.
. . . .
15
1.9 Distribution of A. aculeata in Paraguay. Five terrestrial
ecore-gions present in Paraguay (a) and extent of occurrence and area
of occupancy of Acrocomia aculeata palm. Adapted from Gauto
et al. [
18
].
. . . .
16
1.10 Visit to OISA S.A. factory in August 2020, with the COO Carin
1.12 Oil extraction by hot pressing. Courtesy of OISA S.A.
. . . . .
21
1.13 Coconut endocarp to be used in boilers. Courtesy of OISA S.A.
22
1.14 Product distribution of pyrolytic oil. Adapted from [
19
], with
permission.
. . . .
25
1.15 Competitive biomass pyrolysis scheme.
. . . .
30
1.16 Scheme of a flame front propagation towards reactants.
. . . . .
33
2.1 Coconut endocarp (on the left) and grinded fine particles of
co-conut endocarp (on the right).
. . . .
47
2.2 Thermal analyzer STA F3 Jupiter of NETZSCH
(Source:NET-ZSCH, Operating Instructions Simultaneous TG-DTA/DSC Apparatus
STA 449 F3 Jupiter)
. . . .
49
2.3 Heating program used to perform the thermal degradation analysis
50
2.4 Simplified schematic diagram of the basic components of an
SEM. Adapted from [
20
].
. . . .
51
2.5 Van Krevelen diagram of biomass. Adapted from [
21
].
. . . . .
52
2.6 Schematic diagrams of eight commonly observed adsorption isotherms.
Adapted from [
22
].
. . . .
53
2.7 Dynamic vapour sorption device as a Surface Measurement
Sys-tems. Adapted from [
23
].
. . . .
54
2.8 Schematic of the experimental process.
. . . .
55
2.9 (a) Stainless steel reactor. (b) Tubular furnace to pyrolysis
pro-cess. [
18
].
. . . .
56
3.1 Anhydrous mass loss of coconut endocarp, as a function of time,
for each pyrolysis treatment. The red lines indicate the
temper-ature evolution as function of time.
. . . .
70
3.2 Comparison of DTG curves for (a) untreated and 250 °C-char,
(b) 300 °C-char and 350 °C-char, and (c) 450 °C-char and 550
°C-char.
. . . .
72
3.3 (a) van Krevelen plot. (b) O/C and H/C ratios as function of
the fml.
. . . .
75
3.4 (a) Adsorption isotherms for the untreated and treated samples.
(b) Pore size distribution (PSD) by Density functional theory
(DFT) for untreated and treated samples (Below). (c)
Amplifi-cation of PSD for the untreated and chars treated until 400 °C,
from 10 to 15 Å, and (d) from 25 until 200 Å.
. . . .
77
3.5 Morphological and structural changes over a single particle for
the lower (a-b) and higher (c-d) temperature of treatment.
. . .
78
3.6 SEM/FEG micrographs of (a) coconut endocarp and its chars
3.8 Absolute hysteresis of coconut endocarp and its chars at 0-90 %
of RH.
. . . .
81
4.1 Three-step model fitting
. . . .
93
4.2 Different fractions of 3-step model.
. . . .
95
4.3 (a) Curve adjustment considering two Gaussian distribution model.
96
4.4 (a) Volatile fractions of the model, for the two Gaussian curve.
(b) Volatiles emitted as a function of activation energy, for the
isotherms.
. . . .
97
4.5 (a) Curve adjustment considering three Gaussian DAEM
distri-butions.
. . . .
98
4.6 (a) Volatile fractions of the model, for the three Gaussian curve.
(b) Volatiles emitted as a function of activation energy, for the
isotherms.
. . . 100
4.7 (a) Application of a stepped thermal program to 3-step model.
(b) Application of a stepped thermal program to three Gaussian
DAEM.
. . . 102
5.1 Scheme of the components of the WV generator (left) combined
with the system for thermal analyzer with a WV Furnace (right).
109
5.2 (a) Comparison between TG curves and (b) Char conversion
of coconut endocarp observed in various atmospheres (N
2and
WV). The red dashed line in (a) indicate the temperature
evo-lution as function of time.
. . . 111
5.3 Pore size distribution for (a) sample 1, (b) sample 2 and (c)
sample 3, for a conversion at t
0and t
f.
. . . 114
6.1 Bio-oil collected from coconut endocarp pyrolysis
. . . 120
6.2 Total ion chromatograms (TIC) of coconut endocarp pyrolysis
oil: (a) ethyl acetate fraction (b) diethylether fraction and (c)
water fraction of the oil.
. . . 122
6.3 Toluene/air auto-ignition delay as a function and temperature,
for different pressures and equivalence ratios, using the original
scheme of [
13
] and the new combined Schemes A − F .
. . . 138
6.4 Toluene/air auto-ignition delay as a function and temperature,
for different pressures and equivalence ratios, using the original
scheme of Huang et al. [
13
] and the new combined Schemes G − L.
138
6.5 Ethanol/air auto-ignition delay as a function and temperature,
for different pressures and equivalence ratios, using the original
scheme of Christensen and Konnov [
12
] and the new combined
scheme of Christensen and Konnov [
12
] and the new combined
Schemes G − L.
. . . 139
6.7 Acetic acid/air auto-ignition delay as a function and
temper-ature, for different pressures and equivalence ratios, using the
original scheme of Christensen and Konnov [
12
] and the new
combined Schemes A − F .
. . . 140
6.8 Acetic acid/air auto-ignition delay as a function and
temper-ature, for different pressures and equivalence ratios, using the
original scheme of Christensen and Konnov [
12
] and the new
combined Schemes G − L.
. . . 140
6.9
(a) Toluene/air, (b) Ethanol/air and (c) Acetic acid/air laminar flame speeds as a function of equivalence ratio at 1 bar, using new combined Schemes A − F. The original schemes are due to [13] (a) and [12] ((b) and (c)). Results of (a) are compared to experimental data due to [24] at T = 298 K; whereas those of (b) are compared to experimental data due to [25,26and 24] at T = 300 K; and those of (c) are compared to experimental data due to [12] at T = 338 K.. . . 141
6.10
(a) Toluene/air, (b) Ethanol/air and (c) Acetic acid/air laminar flame speeds as a function of equivalence ratio at 1 bar, using new combined Schemes G − L. The original schemes are due to [13] (a) and [12] ((b) and (c)). Results of (a) are compared to experimental data due to [24] at T = 298 K; whereas those of (b) are compared to experimental data due to [25,26and 24] at T = 300 K; and those of (c) are compared to experimental data due to [12] at T = 338 K.. . . 141
6.11 Bio-oil surrogates/air and toluene/air auto-ignition delay as a
function and temperature, for different pressures and equivalence
ratios, using the new combined Scheme K.
. . . 144
6.12 Bio-oil surrogates/air laminar flame speeds as a function of
equiv-alence ratio at 1 bar, using new combined Scheme K. Results
are compared to experimental data due to Dirrenberger et al.
[
24
] at T = 298 K.
. . . 146
6.13 Pure bio-oil and pure diesel auto-ignition delay as a function and
temperature, for different pressures and equivalence ratios, using
the original scheme of [
13
] (diesel) and the new combined Scheme
K
.
. . . 147
6.14 Bio-oil/diesel laminar flame speeds as a function of equivalence
ratio at 1 bar, using new combined Scheme K. Results are
com-pared to experimental data due to Chong and Hochgreb [
27
] at
using the original scheme of [
13
] (n-butanol) and the new
com-bined Scheme K.
. . . 150
6.16 Bio-oil/n-butanol laminar flame speeds as a function of
equiva-lence ratio at 1 bar, using new combined Scheme K. Results are
compared to experimental data due to Veloo and Egolfopoulos
Introduction
The world is moving towards a bio-based economy, where the gradual but
sustainable introduction of biofuels and bioproducts into the global market
is sought. There is a progressive replacement of fossil fuels and petroleum
products, for example, by using mixtures of liquid biofuels for transportation
purposes and others.
Biomass takes an increasingly important role in this transition to a
bio-based economy. This is because it is the main source of renewable raw material
for the generation of these products. The concept of bio-economy, is expected to
gradually affect all industries, where a continuous changeover to more complex
bio-renewable feedstocks like agricultural residues will occur.
The increase in the quality of life and the growth of any nation, means an
increase in its energy requirements, which also leads to an increase in the world
oil price [
29
]. Biofuels, referred to any solid, liquid or gaseous fuels generates
from biomass, emerges as an alternative to cover these high requirements [
30
].
The Acrocomia endocarp has the advantage of being a second generation
feedstock. This agro-industrial waste is generated in great quantity, about 7 ton
per/ha/year [
31
] during the almond and pulp oils production from A. aculeata
fruit. High oil yields (about 4-6 ton oil/ha) and oil properties similar to palm
oil (Elaeis guineensis) [
32
,
33
], which has the 40 % of the market of plant oils
[
34
], have attracted the attention of Acrocomia palm. In addition, the pulp oil,
can be used for biodiesel production and cosmetic applications (pulp of fruits
presented a fat content of about 25.1-32.1 %) and the almond oil for cosmetic
and as edible oil (has a mean fat content of about 59.3-68.9 %) [
35
,
36
,
37
].
of charcoal with high energy density, from the waste of the processing of its
fruits [
34
,
36
,
38
].
Research Motivation
In recent decades, several investigations have been carried out with different
purposes related to A. aculeata [
39
,
18
]. Most of these works have focused on
the performance and quality of the oils extracted from their pulp and almonds
[
37
]. Other reports focus on the combustible properties of the by-products
generated during the processing of their fruit [
40
,
41
,
42
]. Concerning biofuels
production, the focus of the researches were on bio-diesel generation and its
properties from pulp oil, but no in the liquid product of the pyrolysis of its
process residues [
1
].
However, there is a lack of scientific research related to the evaluation of
the by-products of A. aculeata fruit processing, specifically “coconut endocarp”.
Larger scientific research is needed to evaluate the diversity of potential end
products for a biorefinery. In this sense, there is a gap in the literature related to
the evolution in chemical and structural properties of coconut endocarp during
its isothermal pyrolysis. In particular, the charcoal properties will indicate the
more appropriate uses for this material (i.e. as solid fuel, a raw material for
the gasification process, or others).
Furthermore, kinetic parameters of Acrocomia endocarp pyrolysis
pro-cess were not yet determined. Pyrolysis propro-cess can be carried out with the
main purpose of obtaining bio-oil. Physical properties of bio-oils from coconut
endocarp have been analyzed in our previous work [
6
]. However, its
chemi-cal composition was not yet analyzed, and its combustion chemichemi-cal kinetics
mechanism was not yet proposed. Finally, the activated carbon generated from
Acrocomia endocarp have shown very high surface area, and to the best of our
knowledge this is the first time that water vapor has been used as pyrolysis and
gasification agent simultaneously for this feedstock.
Objectives and Layout
This thesis has the following main objectives:
To determine the kinetic parameters of the pyrolysis process, using at
least five temperatures simultaneously.
To evaluate the surface area and porosity of activated carbons obtained
under different slow-pyrolysis/gasification conditions.
To determine the chemical composition of the bio-oil produced from
tor-refied coconut endocarp —Acrocomia aculeata—.
To propose a chemical kinetic mechanic for the bio-oil combustion based
in a surrogate selected from its chemical composition.
Manuscript outline
To achieve the objectives of this work, the general structure of this manuscript
has been organized as follows:
A non-exhaustive review of biomass as a sustainable resource,
empha-sizing the potential of Acrocomia palm as a new feedstock for biorefinery is
presented in Chapter
1
. The general concept of thermochemical process:
py-rolysis, combustion and gasification are presented, where it is included a short
review about the use of bio-oil as a non-conventional fuel and its combustion
characteristics.
Chapter
2
details the experimental procedure, the facilities and the
an-alytical techniques used to obtain the results of the physicochemical evolution
along the thermal decomposition of the endocarp of Acrocomia aculeata fruit
samples and the kinetic mechanic model for the bio-oil combustion of coconut
endocarp.
Chapter
3
presents the experimental procedure and results obtained along
the thermal decomposition of the endocarp of Acrocomia aculeata fruit samples,
before and after 2 h of isothermal pyrolysis in the range 250 to 550
◦C. The
physicochemical evolution measured by techniques as differential
thermogravi-metric (DTG) analysis, elemental analysis, surface area and pore size analyses,
ESEM and SEM/FEG observation and dynamic vapor sorption evaluation.
Overview
This chapter provides a review of the lignocellulosic biomass structure,
the potential of Acrocomia palm as a sustainable source of feedstock
for biorefinery and the physico-chemical properties of coconut endocarp.
The general concept of thermo-chemical processes: pyrolysis,
combus-tion and gasificacombus-tion are also presented, with its respective
theoreti-cal, fundamental and typical product composition. Moreover, a
non-exhaustive review about the use of bio-oil as a non-conventional fuel
and its combustion characteristics are presented.
1.1
World energy demand and biofuel policies
The growth of any nation is directly related to energy consumption. According
to the International Energy Outlook 2018 (IEO2018) the world energy
con-sumption will grow by 21% between 2020 and 2040, which would represent
from 643.5 quadrillion kJ in 2020 to 697.4 quadrillion kJ in 2030 and 779.7
quadrillion kJ in 2040 (Fig.
1.1
), with more than half of the increase attributed
to countries outside the OECD (Organization for Economic Cooperation and
Development), including China and India, where strong economic growth drives
increasing demand for energy [
29
].
This entails an increase in the world oil price, from its current price of
about 60 US-dollars per barrel to more than double by 2040 [
29
].
Figure 1.1: World energy consumption by fuel type, 1990-2040 (quadrillion
British thermal units "Btu", 1 Btu = 1.055 kJ). Source: International Energy
Outlook 2018 - IEO 2018 [
14
].
solid or gaseous fuels that are produced from biomass [
30
].
Thereby, the United States and the European Union have renewable fuel
standards and bio-fuel policies, which have been implemented to promote a
smooth transition to a bio-based economy. The main standards are, Renewable
Fuel Standards (RFSs) by the Unites States, which establish a minimum volume
of biofuels to be used in the national transportation fuel supply [
43
], and the
European Union (EU) Biofuel Policy [
44
].
1.2
Biomass as a sustainable resource
Biomass is any biological material that derives from living matter or that was
recently alive, that is, from animals, plants or plant derived materials and were
produced directly or indirectly by photosynthesis [
45
]. Lignocellulosic biomass
refers to plant stems, whose main constituents are cellulose hemicellulose and
lignin (Fig.
1.2
) as wood and agricultural residues [
15
].
1.2.1
Lignocellulosic biomass structure
The basic components of the lignocellulosic biomass, also called second-generation
feedstocks, are cellulose, hemicelluloses and lignins (see Fig.
1.2
). Apart from
wood produced in forest, the most important world production, they are mostly
derived from agricultural processes, such as wastes (e.g. corn cobs and stover,
wheat straw, rice hulls, etc.) and usually they are combusted in boilers for heat
and electricity, for forage or into croplands [
47
,
48
].
Figure 1.2: Main components of lignocellulose Biomass (reprinted from Rubin
[
15
] with permission).
The plant biomass comprises an enormous variety of polymeric substances
with multifunctional molecular structures. Concerning the chemical structure
of the main components, we can state:
Cellulose
: it is a linear homogeneous structural polysaccharide composed
of D-glucose units in the
4C
1
conformation, with a high molecular-weight (more
4 OH O O H OH 1 H O 4 OH O O H OH 1 H O 4 OH O O H OH 1 H O 4 OH O O H OH 1 H O
Figure 1.3: Chemical structure of cellulose.
Hemicellulose or polyose
: it is considered the second major wood
chem-ical constituent (usually between 25-35 % wt of dry wood), is a ramified
het-erogeneous structural polysaccharides composed of a mixture units of D-xylose,
L-arabinose, D-mannose, D-galactose, D-glucose, 4−O−methyl glucuronic acid
and galacturonic acid residues. The number of repeating saccharide monomers
is lower than cellulose, only about 150. The monosaccharidic composition,
de-pends on the phylogenetic origins of the plant species [
50
].
O O O O H O OH O H O C H3 C O O H O O O H OHH O O O O O CH2OH OH OH OH O O H OHH O
Figure 1.4: Chemical structure of hemicellulose
Lignin
: the third major component of wood is lignin. Lignin derives
pri-marily from three hydroxycinnamyl alcohols, p-coumaryl, coniferyl and sinapyl
alcohols. It is a phenyl propanoid three-dimensional, highly branched polymer,
composed of syringil (S), guaiacyl (G) and p-hydroxyphenyl (H) units. The
internal structure consists of an irregular array of variously bonded "hydroxy-"
and "methoxy" substituted phenylpropane units, which exhibit the p-coumaryl,
coniferyl and sinaphyl structures [
51
,
52
].
Many factors such as type of plants, tissues, cell-type, stages of growth,
and also the environmental conditions can influence in the content, composition,
and structure of the lignin. Lignin compositions from three A. aculeata fruit
parts selected (stalk, epicarp and endocarp) have been studied by [
16
] using
two-dimensional nuclear magnetic resonance (2D-NMR) spectroscopy and analytical
pyrolysis coupled to gas chromatography and mass spectrometry (Py-GC/MS)
(Fig.
1.5
).
Figure 1.5: Main structures present in the lignins from three parts of A.
ac-uleata
fruit by 2D HSQC NMR (reprinted from del Río [
16
] with permission).
A: β − ethers; A’: β − ether structures with acylated (by acetate, benzoate,
p−
hydroxybenzoate or p−coumarate) γ−OH; B: phenylcoumaran; B’:
phenyl-coumarans with p−hydroxybenzoates acylating the γ − OH; C: resinols; C’:
tetrahydrofuran structures formed by β − β
0-coupling of monolignols acylated
called as organic extractives, and small mineral content.
1.2.2
Processes for biomass conversion
Several processes can be used to convert biomass to energy or more value
ma-terials such as chemicals. The concept of biorefinery consists in using biomass
instead of oil for producing energy and chemicals (Fig.
1.6
) [
53
].
CO2 CO2 CO2 CO2 CO2 CO2 CO2 CO2 Biofuels Heat Electricity Chemicals Biomaterials Biomass Biorefinery Industrial residues End-of-life biomaterials
Figure 1.6: Main products of a biorefinery.
The biomass conversion methods are several, such as mechanical (e.g.
biomass size reduction), chemical (e.g. hydrolysis and transesterification),
bio-chemical and thermobio-chemical processes [
53
,
17
].
The thermochemical methods (combustion/incineration, liquefaction,
gasi-fication, and pyrolysis) have important advantages as these methods use the
entire biomass. Thus, reducing pretreatment costs (acid hydrolysis, enzyme
hydrolysis) and the products can be obtained quickly (in a few seconds to an
hour or two) [
17
].
1.2.3
Thermochemical Biorefinery
Several biorefinery concepts have been proposed as three-phase, whole-crop,
green, lignocellulosic feedstock, integrated, two-platform and hybrid
biorefiner-ies [
56
]. Thermochemical biorefinery concept is seen to be a multiproduct plant
based on a platform chemical. The main advantage is its capability to be
com-bined or slightly modified to achieve multiproduct generation [
56
,
57
].
Gas Heat Combustion Incineration Via turbine to produce electricity Syngas Gasification Steam reforming to produce hydrogen Gas Pyrolysis Hydrotermal upgradation Carbonization Liquefaction Gasification Upgradation Char Bio-oil Adsorbents/ catalyst support
Coprocessing with vacuum gas oil to produce fuel/petrochemical feed stocks Hydro processing to produce fuels/chemical Fuel/Chemicals by Fischer-Tropsch Synthesis THERMOCHEMICAL PROCESSES Soil amendment Steam reforming to produce hydrogen Extraction to separate valuable chemicals Hydrogen/ methane Bulk/special ty chemicals Functional porous carbons
The main products, both chemicals and energy carriers, from a
thermo-chemical biorefinery are:
Syngas
: is a mixture of gases (CO and H
2) from which is possible to
produce chemicals (e.g. hydrocarbons C
1to C
50) by Fischer-Tropsch reaction
or biohydrogen [
58
].
Bio-oil
: is a dark liquid, frequently considered as a microemulsion,
ob-tained from the condensed vapors effluents from the pyrolysis process. Bio-oil
has thousand compounds, most of which are oxygenated and very reactive.
Chemically, it is a complex mixture of water, guaiacols, catecols, syringols,
vanillins, furancarboxaldehydes, isoeugenol, pyrones, acetic acid, formid acid,
other carboxilic acids, hydroxyaldehydes, hydroxyketones, sugars and phenolics
compounds [
59
,
60
].
Char, Charcoal or Bio-char
: is defined as charred organic matter that
has many applications depending on its physical and chemical properties. It
can be used as an energy carrier, as an adsorbent and for improvement of the
soil properties [
61
].
1.3
Biofuels and bio based products — An
opportu-nity
The current trend is towards an increase in the requirements of primary energy
in the world (EIA, 2018) [
29
]. In this regard, biofuels emerge as a sustainable
alternative to hydrocarbons in the transport sector.
The conversion of biomass (an abundant carbon-neutral renewable
re-source) to solid, liquid and gases biofuels, promotes a gradual transition from
a petroleum-based to a bio-based society and economy in which, biomass is the
only renewable resource of carbon (compared to the others: solar, wind, water
and geothermal) from which chemicals, materials, and fuels can be produced.
1.3.1
Generation of biofuels
First-generation biofuels: they are mainly bioethanol, biodiesel and biogas,
derived from edible materials such as sugar, starch, vegetable oil or animal
fats. However, biogas can be also derived from feedstocks which are not in
competition with the food and feed industry, such as waste and residues, in
these cases it can be categorized as 2nd generation biofuel. The main producer
countries of these first-generation biofuels are USA, Brazil and the European
Union (Germany, France, Italy, Austria and Sweden) [
62
,
63
]. Despite the
advantages in terms of the production of these biofuels (high sugar and oil
content of the raw materials and their relatively easy conversion into biofuel)
there are other environmental issues (air pollution, acidification, eutrophication,
ozone depletion, land use, etc) to be analyzed. The main problems of these
biofuels, are that there is a direct competition with food for their feedstock
and fertile land and also the high energy and water input required for crop
cultivation and conversion which raises questions about the effective savings of
CO
2emissions and fossil energy consumption [
53
,
64
,
65
].
Second-generation biofuels: they are mainly gases (e.g. CO, CO
2, CH
4and H
2from lignocellulosic biomass) or synthetic liquid biofuels (e.g. Fisher
Tropsch (FT)-diesel from biomass, bio-oil and bioethanol from lignocellulosic
feedstock) derived from non-edible materials such as agricultural and forest
residues and crops grown for biofuel purposes such as perennial grasses,
Jat-ropha curcas L.) [
66
,
67
,
68
].
Finally briefly, the Third-generation biofuels are those derived from
aquatic biomass such as algae and the Fourth-generation biofuels are
de-rived from engineered plants and microorganisms [
49
].
1.3.2
Generation of bio-based products
Nowadays, only about 5% of all chemicals are bio-based [
69
]. The most common
bio-based chemicals are: Succinic, Fumaric and Malic acids; 2,5-Furan
dicar-boxylic acid; 3-Hydroxypropionic acid; Aspartic acid; Glucaric acid; Glutamic
acid; Itaconic acid; Levulinic acid; 3-Hydroxybutyrolactone; Glycerol; Sorbitol;
Xylitol/Arabinitol [
70
]. Its characteristic of high value, lower volume bio-based
chemicals contributes to a bio-based economy since only biofuels would not
provide the necessary economic incentives.
and synthetic rubbers. Harmsen et al, 2014 [
71
] have investigated the possible
routes to produce polymers from biomass, such as those based in lactic acid and
succinic acid. They can be well produced, since the oxygen atoms needed for
these building blocks are already present in the biomass [
71
]. Producing these
materials from biomass instead of fossil resources significantly contributes to
the development of the bio-based economy.
1.4
Acrocomia aculeata
: an alternative oil crop and
feedstock for biorefinery
The South-American palm species Acrocomia aculeata, commonly known as
mbocayá, macaw, macauba or just coconut palm, has attracted the attention
of researchers in recent years, mainly for its great potential as a sustainable
oil crop [
40
,
41
,
42
,
37
]. Although Acrocomia aculeata is a native species of
South America, its distribution spans the tropics and subtropics of Mexico and
Central America as well. Acrocomia aculeata grows in regions that extend from
Mexico to Argentina. In Paraguay, 23 palm species have been identified [
18
],
and the A. aculeata specie fruit (coconut) has been processed since 1940 [
39
].
At present, no other country processes the fruit. Its many potential uses are
shown in Fig.
1.8
.
Concerning vegetable oils demand, it is continuously growing in the food,
energy and chemical sectors. Compared to the oil palm—Elaeis guineensis—,
which has 40 % of the market of plant oils [
34
], A. aculeata is a promising
candidate for the production of plant oils from its high oil yields (about 4-6
Tm oil/ha) and from its oil properties similar to oil palm [
32
,
33
]. The main
commodities are the pulp oil produced in the mesocarp and the kernel or almond
oil produced in the endosperm. On average, the pulp of fruits presented a fat
content of about 25.1-32.1 %, whereas the almond had a mean fat content of
about 59.3-68.9 % and the time for begin its production yield from its first
harvest is around 4-6 years [
35
,
72
,
37
].
Figure 1.8: Potential uses of Acrocomia fruit.
small quantities, its storage stability (higher than Elaeis fruits), its processing
technology is comparably simple and already cost-efficient at a scale of 5000
Tm of fruits per year, its average yield is 20 Tm of fruits per hectare and year,
and a range of valuable by-products with local and international markets [
39
].
1.4.1
Industrialization of A. aculeata fruit in Paraguay
Five terrestrial ecoregions are recognized to be present in Paraguay (Fig.
1.9a
)
[
18
]. A. aculeata palms are distributed mainly in open areas as Savannah
(Cer-rado), and it constitutes the ecoregion with the highest palm species diversity
[
18
].
(a) (b)
From the economic and productive point of view, the importance of this
indigenous palm that has for the country is unquestionable. Since the
begin-ning of the 20th century, the almond oil has been used in Paraguay for the
manufacture of soap. However, the beginnings of the commercial exploitation
for oil is not known with certainty. Even more, the oil was also known in
Eu-rope prior to 1900 and results of chemical examinations of the kernel oil were
reported since 1896 [
74
]. In the 50’s, the production of almond oil reached 2849
Tm and 1125 Tm for pulp oil annually [
74
].
By 1965, the production of almond oil reached 5100 Tm and pulp oil at
5000 Tm [
75
]. Currently, there are at least five coconut oil industries working
in Paraguay (Fig.
1.10
), most of which are concentrated in three departments:
Central, Cordillera and Paraguarí [
75
]. However, they are operating at 60%
of their capacity as presented in Table
1.1
and others were closing due to the
shortage of raw material. Until today, practically the same production of about
5000 Tm, for both almond and pulp oil, are kept.
Figure 1.10: Visit to OISA S.A. factory in August 2020, with the COO Carin
Daher.
The main reason for the decrease in the supply of raw materials is the
low price that collectors receive for each box of coconut. The price paid for a
box of about 45 kg ranges between 2 and 3 USD approximately.
San d + O rg an ic m at te r H u sk e d H u sk ( ≈ 0 ,1 6 Tm ) P u lp + k er n el (alm o n d + en d o car p ) ( ≈ 0 ,4 6 Tm ) R ec ep ti o n o f co co n u t fru it (1 T m) D ry in g (f o r 30 -45 d ay s) D ry c le a n in g -O rg an ic fe rt iliz er D ry air H u m id air K e rn e lo il P u lp ( ≈ 0,3 4 Tm ) K e rn el ca ke K er n e l En d o car p ( ≈ 0 ,3 6 T m ) P u lp s e p ar at io n C ra cki n g P re ss in g Fi lt ra ti o n Se p ar a ti o n o f th e en d o ca rp D ry in g (1 0 0 ° C ) -O rg an ic f er tiliz er -So lid f u el P u lp ca ke P u lp o il -So lid f u e l -C h ar co al -A n im al fe ed -O rg an ic f er tiliz er -Fo o d p ro d u ct s -C o sm et ic s -So ap -A n im al fe ed -O rg an ic fe rt iliz er
Figure 1.11: Processing of A. aculeata in Paraguay.
The process illustrated in the Fig.
1.11
was detailed by the Agric. Eng.
Juan Lionel Vera Benítez
1and corresponds to the one used by the Paraguayan
Au-company “Industrial Aceitera S.A.C.”
2, which began its operation in 1964 and
has a processing capacity of 60 Tm of fruit per day. However, it currently
operates at 50% of its capacity due to the shortage of raw material.
The reception of the raw material is carried out in boxes of about 50 kg,
at a rate of approximately 500 boxes per day. The fruits are arranged in a
barn for drying by natural convection for 30-40 days, in order to facilitate the
detachment of the pericarp. Then, the dried fruit is sent through a conveyor
belt to a table vibratory, in order to remove impurities that accompany the
fruits and fall through its gratings.
The clean and dry fruit is recovered and sent to a pallet system that
separates the husk from the rest of the fruit. The husk is used to feed the
boiler and its ashes are used as a mineral load in one of the by-products “organic
fertilizer” of the process.
Subsequently, the pulp is separated from the kernel by means of a knife
mill. The pulp is then sent to cookers that operate at 100 °C below atmospheric
pressure, to dry the pulp, and then extract its oil by pressing and filtering using
press filters (Fig.
1.12
). Finally, the pulp oil is stored in tanks in order to
maintain its temperature above 20 °C.
In another line of the process, the endocarp is broken by roller mills.
Then, the almond grain separation is done by density difference, in a mixture
of water and kaolin. The less dense almond is separated from the mixture
by means of collectors and they are directed to the cookers that operate in
a vacuum at 100 °C, for drying. Almond oil is extracted by pressing and
subsequently is filtered and storage in heated tanks. The almond and pulp
expeller are used to feed cattle.
As we can see, the endocarp is used in boilers to provide heat in different
parts of the process (Fig.
1.13
). However, the amount of endocarp produced
is greater than that required and due to its composition, there is a potential
to employ it as raw material for the pyrolysis and gasification process and to
obtain high value products and biofuels.
1.4.2
Coconut endocarp as second generation feedstocks
Relevant aspects of feedstocks for a biorefinery are its quality and quantity
available and the required process to convert them efficiently in high value
gust 2019
